This afternoon I went for a ride through the woods and played with the gizmo quite a bit. I finally learned how it actually works. I think I explained it backwards earlier during stovetop testing.
Anyway, the trigger temp and hysteresis setting are relational... for instance, I wanted the fan to kick on at 100 degrees C (212 F) and stay on until the oil temp cooled off to 88 C (190.4 F), so I had to set the hysteresis at 12 C and set the trigger temp at 88 C. So the actual fan relays triggering temp = the trigger setting (88) + the hysteresis setting (12) = 100 degrees C. The fan kicks on at 100 C and kicks off at 88 C like I intended it to so I'm sure I messed up explaining it all earlier... :-)
I also learned that at idle speed the oil appears to cool down faster while the fan is running than at motor RPMs above idle. In fact, if the RPMs are taken up a bit shortly after the fan kicks on the oil temp immediately increases rather than continuing to decrease. So that probably (or might?) indicates that lower oil flow volumes and slower oil velocity through the cooler while idling allows the moving hot oil more time inside the cooler... when it exits it is appearing to be cooling at a faster rate.
When revving the motor though, the oil temp climbs sharply (immediately) a couple degrees and hangs... then falls back at a much slower rate. So I'm thinking the oil cooler capacity might be slightly undersized on my Rancher, as supplied stock by Honda. So two coolers connected in series (or a single larger one) might be a smart option to have on any heavy duty work/performance bike. Ya certainly can't see/learn this kinda stuff using the stock Honda oil temp sensor.
So do I like this gizmo...? A lot? You betcha! It is very sensitive to tiny oil temp changes and very fast to update the displayed temp. It flat out ROCKS! Many, many thanks go to @wheelsquad
for getting a fire lit under this one!!! Now I can't wait to free up enough time to build some more of them! :-)
I have room for one more pic here so thought I'd share what was at least a 12 foot tall Beaver dam last fall...! It looks like the spring meltdown and icejams took about 3-4 feet or more off the top of their 1st big dam (of many, they control about 3/4 mile of that ravine and have lived behind various dams in that ravine for several decades) and left them with a tangled mess to fix and rebuild. If I hadta' guess... they was a generation of slackers behind that dam... :-)